Implement childcare expense deductions and benefits (#540)

* Implement childcare expense deductions and benefits

* debug

* debug

* debug again

* Fix all review findings: Ontario rate table, BC/AB values, federal refs, tests

Critical fixes:
- Ontario CARE: fix rate table (+2pp error from duplicate 0.73 at $22,500),
  rewrite formula to use federal CCED (line 21400), fix income variable
- BC CCFRI: fix preschool $145→$545, add kindergarten $320 category,
  parameterize all hard-coded ages, flatten nested where() to np.select
- Alberta: replace unsourced $200/$250 with actual discrete income bracket
  tables (14 preschool + 10 school-age brackets), remove linear phase-out
- Federal CCED: fix all 7 references to cite ITA s.63 + T778, broaden
  earned income to include self-employment, fix claimant allocation to use
  total income with deterministic tiebreaker for equal-income case

Should-address fixes:
- Migrate changelog to towncrier format (changelog.d/540.added.md)
- Fix 30 parameter descriptions (trailing periods, active voice)
- Add period metadata to 8 parameter files
- Remove scope creep (armed forces deduction from deductions_from_total)
- Change documentation→reference field on all variable files
- Remove np.round() calls, add #page=5 to BC CCFRI PDF references

Tests: 797 passing (11 new boundary/allocation tests added)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Fix Ontario rate thresholds, Alberta subsidy values, and improve references

- Ontario CARE: Add 2024 rate schedule with correct income thresholds
  from ON479-A ($5k steps $40k-$60k, $3.6k steps $60k-$146.4k)
- Alberta school-age: Correct 7 bracket amounts ($348/$311/$275/$238/$201/$165/$128)
- Alberta preschool: Fix 5 brackets off by $1 ($253/$226/$213/$160/$120)
- References: Add subsection detail to ON/CRA citations, BC legislation
  refs, Alberta regulation refs, specific PDF page anchors
- Tests: Fix 9 expected values, add 8 boundary tests (age 6/7, 15/16,
  disabled 17+, BC $111k, AB age 5)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Fix Ontario rate shift, Alberta wrong regulation citations, and metadata

- Ontario rate.yaml: Remove incorrect 2024 rate overrides at $20k-$40k
  (rates unchanged from 2019), fix spurious $42,500 bracket with 2024
  threshold override, add 2019 ON479-A form reference
- Alberta: Replace wrong AR 143/2008 (licensing reg) citations with
  Early Learning and Child Care Act (SA 2007, c E-0.1), fix rate_unit
  to amount_unit in subsidy schedules
- Tests: Update 2 Ontario expected values to match corrected rates

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Fix Ontario rate table, BC ACCB regulation citation, and federal deduction guard

- Ontario rate.yaml: Rewrite brackets to match ON479-A PDFs (2019 and
  2024 are identical). Remove all unnecessary 2024 overrides, fix 27
  wrong 2019 thresholds, remove spurious $42,500 bracket
- BC ACCB: Fix B.C. Reg. 74/2018 (Gypsy Moth pest control) to correct
  B.C. Reg. 74/97 (Child Care Subsidy Regulation) in all 12 files
- Federal: Add max_(0, ...) guard to prevent negative deduction when
  self-employment losses exceed employment income

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Fix claimant income, bracket offsets, references, and add family rates

- Federal CCED: Fix earned income limit to use claimant's income (not
  family total) per ITA s. 63(1)(e). Extract shared claimant logic into
  is_child_care_expense_claimant variable.
- Ontario CARE: Shift all 39 bracket thresholds by +1 to match "more
  than $X" semantics. Fix reference to s. 103.0.3(6).
- BC ACCB: Update 12 files from repealed B.C. Reg. 74/97 to 189/2024.
  Add period metadata, simplify phase-out formula.
- BC CCFRI: Add Family/In-Home rates (group/ and family/ subfolders),
  new is_family_child_care input variable. Remove redundant multiplier.
- Alberta: Replace Act reference with alberta.ca source, add preschool
  discontinuation note and school-age verification note.
- Orphaned params: Document Ontario max_amount and federal
  child_income_limit with metadata notes.
- Tests: Add 8 new edge-case and boundary tests (816 total, all pass).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Format bc_child_care_fee_reduction.py

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: PavelMakarchuk <pavel.ma99@gmail.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: 3 people

changelog.d/540.added.md

@@ -0,0 +1 @@
+Added child care expense deductions and provincial child care benefits (Ontario CARE credit, BC ACCB, BC CCFRI, Alberta subsidy).

policyengine_canada/parameters/gov/cra/deductions/child_care_expense/age_limit.yaml

@@ -0,0 +1,12 @@
+description: The Income Tax Act sets this maximum age for a child to qualify for the child care expense deduction, unless the child has a disability.
+values:
+  2015-01-01: 16
+metadata:
+  unit: year
+  period: year
+  label: Child care expense deduction age limit
+  reference:
+    - title: Income Tax Act, s. 63(3) — definition of "eligible child" — Maximum age without disability
+      href: https://laws-lois.justice.gc.ca/eng/acts/I-3.3/section-63.html
+    - title: CRA T778 Child Care Expenses Deduction (2024), Part A — Eligible child age limit
+      href: https://www.canada.ca/content/dam/cra-arc/formspubs/pbg/t778/t778-24e.pdf#page=2

policyengine_canada/parameters/gov/cra/deductions/child_care_expense/child_income_limit.yaml

@@ -0,0 +1,16 @@
+description: The Income Tax Act sets this maximum net income for an eligible child claiming the child care expense deduction.
+values:
+  2023-01-01: 15_000
+  2024-01-01: 15_705
+metadata:
+  unit: currency-CAD
+  period: year
+  label: Child income limit for child care expense deduction
+  note: "Documents ITA s. 63(3)(b) child income limit. Not used in formula — implementing this check would create a circular dependency (child's net income depends on the deduction being calculated)."
+  reference:
+    - title: Income Tax Act, s. 63(3) — definition of "eligible child", paragraph (b)
+      href: https://laws-lois.justice.gc.ca/eng/acts/I-3.3/section-63.html
+    - title: CRA T778 Child Care Expenses Deduction (2024) — Eligible child income limit
+      href: https://www.canada.ca/content/dam/cra-arc/formspubs/pbg/t778/t778-24e.pdf#page=2
+    - title: CRA T778 Child Care Expenses Deduction (2023) — Eligible child income limit
+      href: https://www.canada.ca/content/dam/cra-arc/formspubs/pbg/t778/t778-23e.pdf#page=2

policyengine_canada/parameters/gov/cra/deductions/child_care_expense/earned_income_fraction.yaml

@@ -0,0 +1,12 @@
+description: The Income Tax Act limits the child care expense deduction to this fraction of the claimant's earned income.
+values:
+  2015-01-01: 0.6667
+metadata:
+  unit: /1
+  period: year
+  label: Earned income fraction for child care expense deduction
+  reference:
+    - title: Income Tax Act, s. 63(1) — paragraph (e) — Two-thirds earned income limit
+      href: https://laws-lois.justice.gc.ca/eng/acts/I-3.3/section-63.html
+    - title: CRA T778 Child Care Expenses Deduction (2024), Part D — Earned income fraction
+      href: https://www.canada.ca/content/dam/cra-arc/formspubs/pbg/t778/t778-24e.pdf#page=4

policyengine_canada/parameters/gov/cra/deductions/child_care_expense/limit/age_threshold.yaml

@@ -0,0 +1,12 @@
+description: The Income Tax Act sets this age threshold that determines the annual child care expense amount per eligible child.
+values:
+  2015-01-01: 7
+metadata:
+  unit: year
+  period: year
+  label: Age threshold for child care expense limits
+  reference:
+    - title: Income Tax Act, s. 63(3) — definition of "annual child care expense amount" — Age threshold between limit tiers
+      href: https://laws-lois.justice.gc.ca/eng/acts/I-3.3/section-63.html
+    - title: CRA T778 Child Care Expenses Deduction (2024), Part B — Age threshold for expense limits
+      href: https://www.canada.ca/content/dam/cra-arc/formspubs/pbg/t778/t778-24e.pdf#page=3

policyengine_canada/parameters/gov/cra/deductions/child_care_expense/limit/disabled.yaml

@@ -0,0 +1,12 @@
+description: The Income Tax Act sets this maximum annual child care expense amount for a child eligible for the disability tax credit.
+values:
+  2015-01-01: 11_000
+metadata:
+  unit: currency-CAD
+  period: year
+  label: Child care expense limit for children with disabilities
+  reference:
+    - title: Income Tax Act, s. 63(3) — "annual child care expense amount", paragraph (a) — Limit for disabled child
+      href: https://laws-lois.justice.gc.ca/eng/acts/I-3.3/section-63.html
+    - title: CRA T778 Child Care Expenses Deduction (2024), Part B — Limit per disabled child
+      href: https://www.canada.ca/content/dam/cra-arc/formspubs/pbg/t778/t778-24e.pdf#page=3

policyengine_canada/parameters/gov/cra/deductions/child_care_expense/limit/over_7.yaml

@@ -0,0 +1,12 @@
+description: The Income Tax Act sets this maximum annual child care expense amount for a child aged 7 to 16.
+values:
+  2015-01-01: 5_000
+metadata:
+  unit: currency-CAD
+  period: year
+  label: Child care expense limit for children 7-16
+  reference:
+    - title: Income Tax Act, s. 63(3) — "annual child care expense amount", paragraph (c) — Limit for child aged 7 to 16
+      href: https://laws-lois.justice.gc.ca/eng/acts/I-3.3/section-63.html
+    - title: CRA T778 Child Care Expenses Deduction (2024), Part B — Limit per child aged 7 to 16
+      href: https://www.canada.ca/content/dam/cra-arc/formspubs/pbg/t778/t778-24e.pdf#page=3

policyengine_canada/parameters/gov/cra/deductions/child_care_expense/limit/under_7.yaml

@@ -0,0 +1,12 @@
+description: The Income Tax Act sets this maximum annual child care expense amount for a child under age 7.
+values:
+  2015-01-01: 8_000
+metadata:
+  unit: currency-CAD
+  period: year
+  label: Child care expense limit for children under 7
+  reference:
+    - title: Income Tax Act, s. 63(3) — "annual child care expense amount", paragraph (b) — Limit for child under 7
+      href: https://laws-lois.justice.gc.ca/eng/acts/I-3.3/section-63.html
+    - title: CRA T778 Child Care Expenses Deduction (2024), Part B — Limit per child under 7
+      href: https://www.canada.ca/content/dam/cra-arc/formspubs/pbg/t778/t778-24e.pdf#page=3

policyengine_canada/parameters/gov/provinces/ab/benefits/child_care/age_threshold/preschool.yaml

@@ -0,0 +1,11 @@
+description: Alberta applies the preschool child care subsidy schedule to children below this age.
+values:
+  2024-01-01: 5
+metadata:
+  unit: year
+  period: year
+  label: Alberta child care subsidy preschool age threshold
+  note: Preschool parent subsidy was discontinued April 1, 2025, replaced by $15/day Affordability Grant paid to providers. These 2024 rates were valid prior to discontinuation but the official page no longer displays them.
+  reference:
+    - title: Alberta Child Care Subsidy Program — Preschool age eligibility (2024)
+      href: https://www.alberta.ca/child-care-subsidy

policyengine_canada/parameters/gov/provinces/ab/benefits/child_care/age_threshold/school_age_max.yaml

@@ -0,0 +1,11 @@
+description: Alberta applies the school-age child care subsidy schedule to children up to and including this age.
+values:
+  2024-01-01: 12
+metadata:
+  unit: year
+  period: year
+  label: Alberta child care subsidy school-age maximum age
+  note: Age threshold for school-age subsidy (kindergarten through grade 6).
+  reference:
+    - title: Alberta Child Care Subsidy Program — School-age age eligibility (2024)
+      href: https://www.alberta.ca/child-care-subsidy